re=/(?<=<table.*?)(<p>)(?=.*?<//table>)/gi;
alert (sourcestr.replace(re,"<br>"));
<script type="text/javascript">
var str="<p> <table> <p> ,<p> </table> <p> <table> <p> <p> </table> <p> <table> <p> <p> </table>";
var patt=/<table[^>]*>[/s/S]*?<//table>/i;
var wrapper_result=str.split(patt);
var inner_result = str.match(/<table[^>]*>[/s/S]*?<//table>/ig);
var len=inner_result.length;
var final=wrapper_result[0];
for (i=0; i<len; i++)
{
tmp=inner_result[i].replace(/<p>/gi,"<br>");
final+=tmp+wrapper_result[i+1];
}
alert(final);
</script>
alert(sourcestr.replace(/<table.*?//table>/ig, function($1){return $1.replace(/<p>/ig,"<br>")}));
